From b5c72b207baaa33184b23a5a69603f981aaef0c1 Mon Sep 17 00:00:00 2001
From: Jani Nikula <jani.nikula@intel.com>
Date: Tue, 28 Mar 2017 17:59:02 +0300
Subject: [PATCH] drm/i915/dp: return errors from rate_to_index()
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Git-commit: b5c72b207baaa33184b23a5a69603f981aaef0c1
Patch-mainline: v4.13-rc1
References: FATE#322643 bsc#1055900

We shouldn't silently use the first element if we can't find the rate
we're looking for. Make rate_to_index() more generally useful, and
fallback to the first element in the caller, with a big warning.

Cc: Manasi Navare <manasi.d.navare@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/8a6e83b7bf35da0cbbc703ae157944107ff145be.1490712890.git.jani.nikula@intel.com
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/gpu/drm/i915/intel_dp.c |   13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -1513,9 +1513,9 @@ static int rate_to_index(const int *rate
 
 	for (i = 0; i < len; i++)
 		if (rate == rates[i])
-			break;
+			return i;
 
-	return i;
+	return -1;
 }
 
 int
@@ -1533,8 +1533,13 @@ intel_dp_max_link_rate(struct intel_dp *
 
 int intel_dp_rate_select(struct intel_dp *intel_dp, int rate)
 {
-	return rate_to_index(intel_dp->sink_rates, intel_dp->num_sink_rates,
-			     rate);
+	int i = rate_to_index(intel_dp->sink_rates, intel_dp->num_sink_rates,
+			      rate);
+
+	if (WARN_ON(i < 0))
+		i = 0;
+
+	return i;
 }
 
 void intel_dp_compute_rate(struct intel_dp *intel_dp, int port_clock,